1. Field of the Invention
The present invention relates in general to communication systems and components. More particularly the present invention is directed to antenna arrays for cellular communications systems.
2. Description of the Prior Art and Related Background Information
Modern wireless antenna implementations generally include a plurality of radiating elements that may be arranged over a reflector plane defining a radiated (and received) signal beam width and azimuth scan angle. Azimuth antenna beam width can be advantageously modified by varying amplitude and phase of an RF signal applied to respective radiating elements. Azimuth antenna beam width has been conventionally defined by Half Power Beam Width (HPBW) of the azimuth beam relative to a bore sight of such antenna array. In such an antenna array structure radiating element positioning is critical to the overall beam width control as such antenna systems rely on accuracy of amplitude and phase angle of the RF signal supplied to each radiating element. This places severe constraints on the tolerance and accuracy of a mechanical phase shifter to provide the required signal division between various radiating elements over various azimuth beam width settings.
Real world applications often call for an antenna array with beam down tilt and azimuth beam width control that may incorporate a plurality of mechanical phase shifters to achieve such functionality. Such highly functional antenna arrays are typically retrofitted in place of simpler, lighter and less functional antenna arrays while weight and wind loading of the newly installed antenna array can not be significantly increased. Accuracy of a mechanical phase shifter generally depends on its construction materials. Generally, highly accurate mechanical phase shifter implementations require substantial amounts of relatively expensive dielectric materials and rigid mechanical support. Such construction techniques result in additional size and weight not to mention being relatively expensive. Additionally, mechanical phase shifter configurations that have been developed utilizing lower cost materials may fail to provide adequate passive intermodulation suppression under high power RF signal levels.
Consequently, there is a need to provide a simpler method to adjust antenna beam width control.